US3075912A

US3075912A - Hydroconversion of solid carbonaceous materials

Info

Publication number: US3075912A
Application number: US761772A
Authority: US
Inventors: Eastman Du Bois; Warren G Schlinger
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1958-09-18
Filing date: 1958-09-18
Publication date: 1963-01-29
Anticipated expiration: 1980-01-29

Description

Jan- 29 1963 Du Bols EAsTMAN ETAL 3,075,912

HYDROCONVERSION OF SOLID CARBONACEOUS MATERIALS Filed sept. 18. 195e Unite 3,075,912 HYDROCONVERSION F SOLID CARBO- NACEOUS MATERIALS Du Bois Eastman, Whittier, and Warren G. Schlinger,

Pasadena, Calif., assignors to Texaco Inc., a corporation of Delaware Filed Sept. 18, 1953, Ser. No. 761,772 3 Claims. (Cl. 208-8) This invention relates to the hydroconversion of solid carbonaceous materials. The process of the present invention is particularly applicable to the treatment of coal and may be applied to the hydrogenation of anthracite, bituminous coal or lignite. In its more specific aspects, this invention relates to the production of valuable liquids such as fuels for internal combustion engines.

Prior attempts to convert solid carbonaceous materials such as coal into valuable liquid products by hydrogenation have not proven satisfactory. Because of the high pressures which are required and the long reaction times, the equipment necessary for carrying out the reaction has been expensive and cumbersome, e.g. a commercial reactor large enough to allow a reaction time of 3-4 hours would have `an internal diameter of 32 inches and a wall thickness Aof about 8 inches. In addition, the use of a catalyst has presented several problems. Fixed bed catalysts have proven impractical because of the nature of `the material 'being treated. The use of a iinely divided catalyst suspended in the reaction medium has proven costly because of the ineiciency of the known hydrogenation methods. The catalyst rapidly became deactivated by being coated with asphalt and after one pass through the reaction zone hadto be discarded. Also, because of .the inetliciency of Aknown methods, it was necessary, for 'the production of lighter hydrocarbon liquids to hydrogenate the coal in one reactor using a finely divided catalyst, separate the heavy liquid product from the ash and contaminated catalyst, add fresh catalyst'to the heavy liquid product and then subject it to additional hydrogenation in a second reactor to Vproduce a liquid boiling in the gasoline range.

It is an object of the present invention to provide an improved process for the hydrogenation of a solid carbonaceous material.

Another object of the present invention is to provide `an improved process for the production of valuable liquids from coal by reaction of the powdered coal with hydrogen.

Still another object is to provide an improved process for the production of motor fuels from coal by a non- .catalytic hydrogenation process.

In accordance with the process ofthe present invention the solid carbonaceous material such as coal is tinely divided, slurried in a liquid medium such as water ory oil and passed in contact with hydrogen through a reactor under conditions of highly turbulent flow to produce valuable liquid products.

Any solid carbonaceous material Vmay be suitably treated by the process of the present invention. Such materials as anthracite, anthracite silt, bituminous coal, lignite, peat, sawdust and the like are satisfactory feed stocks. The solid carbonaceous'material which will be referred to as'coal in the following general description of the invention is pulverized to an average particle size vof about -60 mesh and is then slurried with a suitable liquid medium which is inert or only slightly reactive under reaction conditions such as water or an oil which may serve as a hydrogen donor. Preferably, theslurrying Ymedium used in forming the suspension is a hydrogenated aromatic or an oil mixture comprising hydroaromatics which act as hydrogen transfer agents. Hydroaromatics which are suitable yfor use in the process include tetralin and decalin. The heavy-oil or middle distillate which are obtained from the hydrogenation of the coal are especially suited for the preparation of the feed mixture and contain hydroaromatics. If desired, a fraction separated from the heavy oil product or a suitable fraction of oil from another source may be used in the preparation of the feed slurry. The slurry will usually contain at least 'about 35% by weight of liquid. To maintain the liquid particles in suspension, the liquid slurry should be maintained at a velocity of aboutl to 10 feet per second depending on the slurry medium and on the average particle size. i

The reaction in which the coal is hydrogenated is carried out ina tubular reactor'having a length of at least 100 and preferably at least times the maximum cross sectional dimension of the reactor.

The hydrogen used in the process of the present invention may be Iderived from any suitable source. Electrolytic hydrogen or hydrogen obtained by the partial combustion of carbonaceous materials has proven satisfactory. Materials suitable for feed stock to a partial combustion gas generator are powdered solid carbonaceous materials, liquid hydrocarbons or gaseous hydrocarbons. Heavy liquid hydrocarbons and hydrocarbon gases which are produced by the hydrogenation of solid carbonaceous materials are particularly desirable. When solid carbonaceous materials containing volatile substances are used as feed stock vto thegas generator, the materials volatilized during the preheating of the solid carbonaceous vmaterial may be removed and, if desired, included inthe feed to the -hydrogenation unit. When materials containing large amounts of moisture such as lignite are used as feed stock for the gas generation, after preheating, a portion of the steam shouldbe removed prior to the introduction of the feed into the generator to prevent the introduction of excessive amounts of steam into the gas generatorA The hydrogen used in the hydrogenation step may bein relatively pure form or may be used in concentrations as low vas 25 volume percent. Synthesis gas, i.e. a mixture vof carbon monoxide and hydrogen such as that obtained by the methods disclosedin U.S. Patents 2,582,938 Vand 2,669,509 may be used satisfactorily.

Reaction times may range from 1 second to 2 hours but reaction times of 20 to 300 seconds are preferred. Teniperatures of 700vto l500 F., preferably between about 900 and 1100" F. may be employed. Superatmospheric pressures ranging from 500 to 20,000 p.s.i.g. Yand higher may be used although pressures of 1500 to 10,000 p.s.i.g. are preferred. Hydrogen rates may range from 1000 to 100,000 standard cubic feet per barrel of slurry feed, rates of 2000 to 50,000 standard cubic feet per barrel-of slurry feed being preferred. Y

For the hydrogenation of the coal to be'effectve Ythe reaction mixture must be maintained/during the reaction, .under conditions of high turbulence. The slurry feed rate, hydrogenl recycle rate, reaction coil diameter and operating conditions of .temperature and pressure all tend to aect the velocity of ow and the turbulence. It has been found convenient to express turbulence in terms of the ratio of the average apparent viscosity of the owing stream, 2m, to the molecularor kinematic viscosity v, viz. 2m

Hereinafter, we shall refer to this ratio as turbulence level. The apparent viscosity of the owing stream, em, equals fthe sum of the eddy viscosity, em,

and the kinematic viscosity v which may be shown in the expression em=emlv. Under conditions of turbulence,

em, has a finite value and it is apparent that if the magnitude of the apparent viscosity exceeds the kinematic viscosity at `the point in question, that the ratio of exceeds unity. The average apparent viscosity, gm, as employed hereinis dened by the equation where ro is the radius of the conduit. By substitution and integration, employing the parameters described by Corcoran et al., Industrial and Engineering Chemistry, 44, 410 (1952), this expression The latter equation is in terms which may be readily determined for a given system; ro being the conduit radius, a the specific weight of the owing fluid, g the acceleration of gravity and the pressure drop per unit of conduit length. In the pro-cess of this invention, turbulence levels of and higher may be employed but turbulence levels of 50 to 1000 are preferable. At turbulence levels below 25, a heavy tarlike material is formed at the expense of the desired products. 'Ihis tar-like material also causes fouling and plugging of the apparatus requiring frequent shut-downs.

In the foregoing paragraph, the various symbols used in the formulas are delned as follows:

d=dilerential g= acceleration of gravity, feet per second p=pressure, pounds per square foot r=radial distance from center of conduit, feet r0=radius of conduit, feet x=distance, feet em=eddy viscosity, square feet per second emr-apparent viscosity, square feet per second may be rewritten em=average apparent viscosity, square feet per second The invention may be better understood by referring to the accompanying drawing which represents diagrammatically a flow scheme `for the practice of the present invention. Y

Coal is introduced through line 21 to grinding mechanism 22 where it is pulverized to an average particle size o-f below about 60 mesh. The powder is transferred through line 23 to mixing chamber 24 wherein it is mixed with oil introduced through line 25. The coal oil slurry is then transferred through line and with hydrogen from line 31 isintroduced into preheater 32 where the temperature is raised 'to about SOO-600 F.

aendern The heated slurry and hydrogen are then passed through line 33 to hydrogenation unit 34 Where they are subjected to highly turbulent ow. The hydrogenation product is removed from hydrogenation unit 34 through line 35 and introduced into hot separator 36 where gaseous material is separated from the liquid product. The liquid product is transferred to let down tank 40 through line 41. In let down tank 40, the pressure is reduced and a separation is effected between the heavy oil and the oil saturated residue. The heavy oil is removed from let down tank dit through line 43 and may be returned to slurry tank 24 through lines 46 and 25 or sent to gas generator 80 by means of

lines

43, 38 and 81. The heavy oil saturated ash is sent to ash separator 50 through line 51 Where the heavy oil is separated to a large extent from the ash which is removed from ash separator 50 through line 52, the oil being withdrawn through line 79. Ash separator 50 may be either in the form of a centrifuge or in the form of a separating tank containing a lower layer of water. In either case, dilution of the heavy oil with a lighter oil is preferred in the irst case to facilitate the removal of the ash and in the second case to minimize the possibility of the formation of oil-water emulsions. The overhead from hot separator 36 is withdrawn through line 61 and after cooling in a heat exchanger (not shown) is sent to cold separator 62 from which hydrogen is withdrawn through line 31 and returned to preheater 32 through line 30. The liquid hydrogenation product is removed from cold separator 62 through line 63 and introduced into fractionator 64 wherein a separation is made of light hydrocarbon gases withdrawn through line 65, a motor fuel fraction withdrawn through line 66, a middle distillate fraction withdrawn through line 67 and a residual fraction withdrawn through line 68. When a portion of the middle distillate is used to dilute the heavy residue withdrawn from let down tank 40 through line 51 it is sent through

lines

67, 81, 46, 70 and 51 to ash separator 50 Where it facilitates the separation of the heavy oil from the ash. If desired, a portion of the middle distillate from fractionator 64 may be used to form a slurry of the coal feed, in which case it is sent to mixing chamber 24 through

lines

67, 81, 46 and 25.

Hydrogen for the process is preferably supplied by partial combustion of the heavy liquid products resulting from the hydrogenation of the coal. Heavy oil from ash separator 50 for the bottoms from fractionator 64 or a portion of the middle distillate from fractionator 64 may be sent to generator through

lines

79 and 81, 68 and 81 or 67 and 81 respectively or a mixture thereof may be used as feed to gas generator 80. Steam from line 84 and oxygen from line 85 are also introduced into gas generator 80 where the oil is subjected to partial combustion. The products are removed from generator 80 through line 89 and partially cooled in heat recovery unit 85, which may be, for example, a heat exchanger in which the hot gaseous products are passed in indirect heat exchange with water. The resulting steam may be used as a source of power for the grinding operation. The product gases then may be sent through to preheater 32 by rneans of

lines

86, 87, 90 and 30 or if a high concentration of hyodrogen is desired, may be subjected to a water gas shift in shift reactor 91 Where the partial conibustion products are contacted with an iron oxide catalyst in the presence of steam, the carbon monoxide reacting with steam to produce carbon dioxide and additional hydrogen. The shifted gas is transferred through line 92 to scrubber 93 wherein the gas is contacted with an amine solution for the removal of CO2 and a gas containing about 95% hydrogen is removed and sent to preheater 32 through

lines

90 and 30.

The following example is given for illustrative purposes only and it should be understood that the invention is not limited thereto.

A slurry composed of 10 parts by weight of bituminous coal pulverized to a particle size of -60 mesh and 11 parts by weight of a middle distillate, the source of which will be explained later, is mixed with 10,000 cubic feet of a gas containing 80% hydrogen per barrel of slurry. The mixture is passed through a tubular reactor at a temperature of 950 F., a pressure of 5000 p.s.i.g., a reaction time of 50 seconds and at a turbulence level of 450. The hydrogen containing gas is made up of 7640 standard cubic feet of recycle gas and 2360 standard cubic feet of make-up hydrogen having a purity of 95%. After hot and cold separation, let down, centrifuging and fractionating, the products obtained per 100 lb. of coal feed are as follows:

Hydrogen consumption amounts to 1400 standard cubic feet per 100 lb. coal feed.

Of the 130 pounds of middle distillate, 110 pounds is recycled per 100 1b. of coal feed to make up additional slurry, pounds is withdrawn to storage and the remaining 10 pounds together with 20.5 pounds of heavy oil are charged with 15.2 pounds of steam and 31.5 pounds of oxygen to a synthesis gas generator. The gas generator is opera-ted at 290 p.s.i.g. and 2400 F. After quenching, the eiiluent gases are passed to a shift converter and then contacted with an amine scrubber. The product gas amounts to 1400 standard cubic feet of 98% purity hydrogen which is used as make up for the hydrogenation unit. The gasoline produced has the following characteristics.

This gasoline may be upgraded, by catalytic reforming, to produce a motor fuel having a leaded octane number of about 100.

Obviously, many other modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for the hydroconversion of a solid carbonaceous material which comprises forming a slurry of said solid carbonaceous material with a hydrocarbon liquid boiling in the middle distillate range, passing said slurry as a confined stream through a hydrogenation zone maintained at a temperature between about 700 and 1500 F., a pressure between -about 1500 and 10,000 p.s.i.g. and a turbulence level of between about 50 and 1000 in the presence of hydrogen, separating the eluent from said hydrogenation zone into a gas containing hydrogen, a fraction containing hydrocarbon gases, a fraction boiling in the motor fuel range, a fraction boiling in the middle distillate range and a heavy oil, recycling said gas containing hydrogen to the hydrogenation zone, recycling at least a portion of said fraction boiling in the middle distillate range to form additional slurry, forming a second slurry `of finely-divided solid carbonaceous material with at least a portion of said heavy oil, subjecting said second slurry to partial combustion to produce agas containing hydrogen and carbon monoxide, blending a portion of said gas containing hydrogen and carbon monoxide with said fraction containing hydrocarbon gases to produce a gas suitable for use as a heating gas, subjecting the balance of said gas containing hydrogen and carbon monoxide to a water gas shift reaction to produce a hydrogen rich gas and introducing said hydrogen rich gas into the hydrogenation zone as make-up hydrogen.

2. The process of claim l in which the temperature is 900-1100 F.

3. The process of claim 1 in which the solid carbonaceous material comprises coal.

References Cited in the file of this patent UNITED STATES PATENTS 1,458,983 Kirby June 19, 41923 1,888,998 Mercier Nov. 29, 1932 2,007,226 Szayna July 9, 1935 2,207,494 Viktora July 9, 1940 2,639,982 Kalbach May 26, 1953 2,658,861 Pevere et al Nov. 10, 1953 2,753,296 Sellers July 3, 1956 2,793,104 Rees May 21, 1957 2,885,337 Keith et a-l May 5, 1959 2,989,461 Eastman et al. June 20, 1961

Claims

1. A PROCESS FOR THE HYDROCONVERSION OF A SOLID CARBONACEOUS MATERIAL WHICH COMPRISES FORMING A SLURRY OF SAID SOLID CARBONACEOUS MATERIAL WITH A HYDROCARBON LIQUID BOILING IN THE MIDDLE DISTILLATE RANGE, PASSING SAID SLURRY AS A CONFINED STREAM THROUGH A HYDROGENATION ZONE MAINTAINED AT A TEMPERATURE BETWEEN ABOUT 700 AND 1500*F., A PRESSURE BETWEEN ABOUT 1500 AND 10,000 P.S.I.G. AND A TURBULENCE LEVEL OF BETWEEN ABOUT 50 AND 1000 IN THE PRESENCE OF HYDROGEN, SEPARATING THE EFFLUENT FROM SAID HYDROGENATION ZONE INTO A GAS CNTAINING HYDROGEN, A FRACTION CONTAINING HYDROCARBON GASES, A FRACTION BOILING IN THE MOTOR FUEL RANGE, A FRACTION BOILING IN THE MIDDLE DISTILLATE RANGE AND A HEAVY OIL, RECYCLING SAID GAS CONTAINING HYDROGEN TO THE HYDROGENATION ZONE, RECYCLING AT LEAST A PORTION OF SAID RRACTION BOILING IN THE MIDDLE DISTILLATE RANGE TO FORM ADDITIONAL SLURRY, FORMING A SECOND SLURRY OF FINELY-DIVIDED SOLID CARBONACEOUS MATERIAL WITH AT LEAST A PORTION OF SAID HEAVY OIL, SUBJECTING SAID SECOND SLURRY TO PARTIAL COMBUSTION TO PRODUCE A GAS CONTAINING HYDROGEN AND CARBON MONOXIDE, BLENDING A PORTION OF SAID GAS CONTAINING HYDROGEN AND CARBON MONOXIDE WITH SAID FRACTION CONTAINING HYDROCARBON GASES TO PRODUCE A GAS SUITABLE FOR USE AS A HEATING GAS, SUBJECTING THE BALANCE OF SAID GAS CONTAINING HYDROGEN AND CARBON MONOXIDE TO A WATER GAS SHIEFT REACTION TO PRODUCE A HYDROGEN RICH GAS AND INTRODUCING SAID HYDROGEN RICH GAS INTO THE HYDROGENATION ZONE AS MAKE-UP HYDROGEN.